Dental glass and dental composition

ABSTRACT

A dental glass includes, in terms of oxide:phosphorus (P 2 O 5 ) by greater than or equal to 40% by mass and less than or equal to 70% by mass; potassium (K 2 O) by greater than or equal to 20% by mass and less than or equal to 40% by mass; and calcium (CaO) by greater than or equal to 1% by mass and less than or equal to 20% by mass, wherein the dental glass does not substantially contain silicon and aluminum.

TECHNICAL FIELD

The present invention relates to a dental glass and a dentalcomposition.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application and claimspriority under 35 U.S.C. 120 to U.S. patent application Ser. No.16/315,781 filed on Jan. 7, 2019, which is the National Stage ofInternational Application No. PCT/JP2017/024481 filed on Jul. 4, 2017,which claims priority to Japanese Patent Application No. 2016-140440,filed on Jul. 15, 2016. The contents of the applications areincorporated herein by reference in their entirety.

BACKGROUND ART

In a dental composition such as a dental cement, a dental compositeresin, and a dental adhesive, a dental glass is occasionally blended.This is because, by blending a dental glass in a dental composition, notonly an effect of enhancing the strength but also an effect due to ionsin the dental glass can be obtained.

As an effect due to ions in the dental glass, specifically, for example,aluminum ions can be cured by reacting with an acid solution (glassionomer cement). In addition, by being released in a mouth and absorbedby teeth, fluoride ions are expected to have effects of strengtheningthe teeth and preventing dental carries. Calcium ions and phosphate ionsare also expected to have effects of remineralizing teeth and preventingdental carries by being absorbed by the teeth.

Therefore, as disclosed in, for example, Patent Document 1 to PatentDocument 3, a dental glass containing calcium or phosphorus (alsoreferred to as physiologically active glass composition, bioactive glassor the like) and a dental composition in which a dental glass is mixedare conventionally known.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese National Publication of InternationalPatent Application No. 2004-521135

[Patent Document 2] Japanese National Publication of InternationalPatent Application No. 2008-520565

[Patent Document 3] Japanese Patent No. 5020833

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, in conventional dental glasses, the property of releasingcalcium ion and phosphate ion is not necessarily high, and the effectsof remineralizing teeth and preventing dental carries are notsufficient.

The present invention is made in view of the problem of conventionaltechniques described above, and an object in one aspect of the presentinvention is to provide a dental glass that is excellent in a propertyof releasing calcium ions and phosphate ions.

Means for Solving the Problem

According to one aspect of the present invention, a dental glassincludes, in terms of oxide:phosphorus (P₂O₅) by greater than or equalto 40% by mass and less than or equal to 70% by mass; potassium (K₂O) bygreater than or equal to 20% by mass and less than or equal to 40% bymass; and calcium (CaO) by greater than or equal to 1% by mass and lessthan or equal to 20% by mass, wherein the dental glass does notsubstantially contain silicon and aluminum.

Effects of the Invention

According to one aspect of the present invention it is possible toprovide a dental glass that is excellent in a property of releasingcalcium ions and phosphate ions.

EMBODIMENT FOR CARRYING OUT THE INVENTION

In the following, an embodiment for carrying out the present inventionwill be described. The present invention is not limited to the followingembodiment, and various modifications and substitutions can be made forthe following embodiment without departing from the scope of the presentinvention.

[Dental Glass]

In the present embodiment, a configuration example of a dental glasswill be described.

A dental glass according to the present embodiment can containphosphorus; sodium and/or potassium; and calcium.

Further, it is possible to contain, in terms of oxide, phosphorus (P₂O₅)by greater than or equal to 40% by mass and less than or equal to 70% bymass; sodium and/or potassium (Na₂O, K₂) by greater than or equal to 20%by mass and less than or equal to 40% by mass; and calcium (CaO) bygreater than or equal to 1% by mass and less than or equal to 20% bymass.

Also, it is preferable not to substantially contain silicon andaluminum.

Because calcium ions and phosphate ions are expected to have effects ofremineralizing teeth and preventing dental carries by being absorbed bythe teeth, the inventors of the present invention have conducted earneststudies on a dental glass that is excellent in a property of releasingcalcium ions and phosphate ions. As a result, the inventors of thepresent invention have found that a dental glass containing phosphorus(P); one or more kinds selected from sodium (Na) and potassium (K); andcalcium (Ca) at a predetermined ratio enables to release a largequantity of ions such as calcium ions and phosphate ions, completed thepresent invention.

As described above, the dental glass according to the present embodimentcan contain phosphorus (P), in terms of oxide (P₂O₅), by greater than orequal to 40% by mass and less than or equal to 70% by mass. This isbecause the solubility of the dental glass in water can be increasedwhen the content of P is greater than or equal to 40% by mass in termsof oxide. However, in order to sufficiently secure the content of othercomponents, the content of P is preferably less than or equal to 70% bymass in terms of oxide. Phosphate ions released from the dental glasshave effects of remineralizing teeth and preventing dental carries. Thecontent of P in the dental glass according to the present embodiment ismore preferably greater than or equal to 53% by mass and less than orequal to 70% by mass in terms of oxide.

Also, the dental glass according to the present embodiment can containsodium (Na) and/or potassium (K), in terms of oxide (Na₂O, K₂O), bygreater than or equal to 20% by mass and less than or equal to 40% bymass. This is because the solubility of the dental glass in water can beincreased by containing Na and/or K, in terms of oxide, by greater thanor equal to 20% by mass and less than or equal to 40% by mass. However,in order to sufficiently secure the content of other components, thecontent of Na and/or K is preferably less than or equal to 40% by massin terms of oxide. Sodium ions and/or potassium ions released from thedental glass have an effect of adjusting a pH value suitable forremineralizing teeth and preventing dental carries. The content of Naand/or K in the dental glass according to the present embodiment is morepreferably greater than or equal to 25% by mass and less than or equalto 40% by mass in terms of oxide. Note that in a case of containing bothNa and K, it is preferable that the total content of both components isin the above range in terms of oxides.

Also, the dental glass according to the present embodiment can containcalcium (Ca), in terms of oxide (CaO), by greater than or equal to 1% bymass and less than or equal to 20% by mass. This is because, when thecontent of Ca is greater than or equal to 1% by mass in terms of oxide,it is possible to secure a sufficient release amount of calcium ionsfrom the dental glass. However, in order to sufficiently secure thecontent of other components, the content of Ca is preferably less thanor equal to 20% by mass in terms of oxide. Calcium ions released fromthe dental glass have effects of remineralizing teeth and preventingdental carries. The content of Ca in the dental glass according to thepresent embodiment is more preferably greater than or equal to 2% bymass and less than or equal to 15% by mass.

Also it is preferable that the dental glass according to the presentembodiment does not substantially contain silicon and aluminum. This isbecause if silicon and/or aluminum are contained, the solubility of thedental glass in water decreases. Note that not substantially containingit means not intentionally adding it in the dental glass, and does notexclude, for example, an impurity in a production step that is mixed asan inevitable component mixed. For example, it means that in terms ofoxide, the respective contents of silicon and aluminum are less than 1%by mass. In particular, the total content of silicon and aluminum ispreferably less than 1% by mass in terms of oxide.

The dental glass according to the present embodiment can also containoptional components in addition to the components described above.

The dental glass according to the present embodiment can contain, forexample, strontium (Sr), in terms of oxide (SrO), by greater than orequal to 0% by mass and less than or equal to 20% by mass. When thedental glass according to the present embodiment contains Sr, aradiopacity can be added to the dental glass.

The dental glass according to the present embodiment can contain, forexample, lanthanum (La), in terms of oxide (La₂O₃)), by greater than orequal to 0% by mass and less than or equal to 20% by mass. When thedental glass according to the present embodiment contains La, aradiopacity can be added to the dental glass.

The dental glass according to the present embodiment can contain, forexample, boron (B), in terms of oxide (B₂O₃), by greater than or equalto 0% by mass and less than or equal to 10% by mass. When the dentalglass according to the present embodiment contains B, an antibacterialproperty can be added to the dental glass.

The dental glass according to the present embodiment can contain, forexample, zinc (Zn), in terms of oxide (ZnO), by greater than or equal to0% by mass and less than or equal to 10% by mass. When the dental glassaccording to the present embodiment contains Zn, an antibacterialproperty can be added to the dental glass.

The dental glass according to the present embodiment can contain, forexample, silver (Ag), in terms of oxide (AgO), by greater than or equalto 0% by mass and less than or equal to 10% by mass. When the dentalglass according to the present embodiment contains Ag, an antibacterialproperty can be added to the dental glass.

The dental glass according to the present embodiment can contain, forexample, fluorine (F) by greater than or equal to 0% by mass and lessthan or equal to 20% by mass. When the dental glass according to thepresent embodiment contains F, an effect of preventing dental carriescan be added to the dental glass.

Also it is preferable that the dental glass according to the presentembodiment does not substantially contain sulfur (S). This is because ina case where the dental glass according to the present embodimentcontains S, it may cause an odor in a mouth. Note that, as describedabove, not substantially containing it means not intentionally adding itin the dental glass, and does not exclude, for example, an impurity in aproduction step that is mixed as an inevitable component mixed. Thecontent of S in the dental glass according to the present embodiment ispreferably less than 1% by mass.

Also it is preferable that the dental glass according to the presentembodiment does not substantially contain iron (Fe). This is because ina case where the dental glass according to the present embodimentcontains Fe, it may cause tooth discoloration in a mouth. Note that, asdescribed above, not substantially containing it means not intentionallyadding it in the dental glass, and does not exclude, for example, animpurity in a production step that is mixed as an inevitable componentmixed.

The content of Fe in the dental glass according to the presentembodiment is preferably less than 1% by mass. The pH of the dentalglass according to the present embodiment when dissolved in water ispreferably greater than or equal to 5 and less than or equal to 11, andis more preferably greater than or equal to 6 and less than or equal to10. This is because when the pH is less than 5 or exceeds 11 it is notsuitable for use in a mouth.

Note that the pH when a dental glass is dissolved in water can be a pHafter a dental glass pulverized to have an average particle diameter of10 μm, the pulverized glass is dispersed in distilled water so as tohave a concentration of 1% by mass (input dental glass mass), andstirred at an ambient temperature for 1 hour.

Here, the average particle diameter means a particle diameter at anintegrated value 50% in a particle size distribution obtained by a laserdiffraction/scattering method, and has a similar meaning in other partsof the present specification.

The solubility of the dental glass according to the present embodimentin water is preferably greater than or equal to 10%.

Note that the solubility of a dental glass in water can be evaluated bythe following procedure.

First, a dental glass pulverized to have an average particle diameter of10 μm is dispersed in distilled water so as to have a concentration of1% by mass (input dental glass mass), and stirred at an ambienttemperature for 0.1 hour. Next, undissolved glass powder is recoveredwith filter paper. Then, the mass of the undissolved dental glass afterbeing dried (undissolved dental glass mass) is measured, and thesolubility of the dental glass in water is calculated by the followingformula (1).

(solubility of dental glass in water (mass %))=[(input dental glassmass)−(undissolved dental glass mass)]/(input dental glassmass)−100  Formula (1)

The method of producing the dental glass according to the presentembodiment described above is not particularly limited. For example, adental glass can be produced by weighting and mixing materials so as tomake a predetermined composition dental glass, heating it to be greaterthan or equal to the melting point of the materials, melting it to behomogeneous, and thereafter rapidly cooling it by a process such as aprocess of putting the melt into water or a twin-roll process. Also,various glass producing methods such as a sol-gel method can be used.Note that the obtained dental glass may also be subjected to apulverization treatment so as to have a desired particle diameterdepending on the intended use. A preferable configuration example of themethod of producing the dental glass according to the present embodimentwill be described later below.

According to the dental glass according to the present embodiment,because of containing P, Na and/or K, and Ca to be at respectivepredetermined contents and not substantially containing silicon andaluminum, it is possible to make a dental glass whose pH when beingdissolved n water is in a range suitable for use in a mouth and whosesolubility in water is high and that is excellent in a property ofreleasing calcium ions and phosphate ions.

The dental glass according to the present embodiment can also be used,for example, as a component of a dental composition. That is, a dentalcomposition containing the dental glass according to the presentembodiment can be made. Note that examples of the dental compositioninclude, but are not limited to, a dental cement (conventionalresin-modified glass type ionomer cement, resin cement), a dentalbonding agent, a dental primer, a dental coating material, a dentalcomposite resin, a dental indirect composite, a CAD/CAM composite block,a temporary restorative material, a dental filler, a dentifrice, and thelike.

In this case, components other than the dental glass contained in thedental composition are not particularly limited, and various componentscan be contained in accordance with the purpose or the like of thedental composition or the like.

Examples of components other than the dental glass that can be containedin the dental composition include a filler, a (meth)acrylate, a solvent,a polymerization initiator, a stabilizer, a pigment, and the like.

As the filler, for example, one or more kinds selected from silica suchas fumed silica, alumina, hydroxyapatite, titanium oxide, yttrium oxide,zirconia, fluoroaluminosilicate glass, barium glass, lanthanum glass,strontium glass, quartz glass, and the like can be preferably used. Notethat the filler may be treated, as needed, with a surface treatmentagent such as a silane coupling agent.

Also, the above-described (meth)acrylate means various monomers,oligomers, or prepolymers of acrylate or methacrylate, and may have oneor more methacryloyloxy groups or acryloyloxy groups.

As the solvent, one or more kinds selected from, for example, ethanol,propanol, methyl ethyl ketone, acetone, and the like can be preferablyused.

According to the dental composition according to the present embodiment,because of containing the above-described dental glass, it is possibleto make a dental composition that is excellent in a property ofreleasing calcium ions and phosphate ions.

[Method of Producing Dental Glass]

Next, a configuration example of a method of producing the dental glassaccording to the present embodiment will be described. Note that, by themethod of producing the dental glass according to the presentembodiment, the dental glass described above can be produced. Hence, apart of the description already described will be omitted.

In the method of producing the dental glass according to the presentembodiment, the dental glass can be produced by melting a materialcomposition and thereafter pulverizing the material composition.

As described above, the dental glass according to the present embodimentcan contain phosphorus, sodium and/or potassium, and calcium. Therefore,the material composition can contain materials corresponding tophosphorus, sodium and/or potassium, and calcium.

Although a material corresponding to phosphorus is not particularlylimited, for example, one or more kinds selected from phosphoric acid,sodium phosphate, potassium phosphate, calcium phosphate, strontiumphosphate, sodium dihydrogen phosphate, and the like can be preferablyused as the material corresponding to phosphorus. Note that two or morekinds selected from the above compound group may be used in combination.

Although a material corresponding to sodium is not particularly limited,for example, one or more kinds selected from sodium phosphate, sodiumdihydrogen phosphate, sodium carbonate, sodium hydrogen carbonate,sodium fluoride, and the like can be preferably used as the materialcorresponding to sodium. Note that two or more kinds selected from theabove compound group may be used in combination.

Although a material corresponding to potassium is not particularlylimited, for example, one or more kinds selected from potassiumphosphate, potassium fluoride, potassium carbonate, potassiumbicarbonate, dipotassium hydrogenphosphate, and the like can bepreferably used as the material corresponding to calcium. Note that twoor more kinds selected from the above compound group may be used incombination.

Although a material corresponding to calcium is not particularlylimited, for example, one or more kinds selected from calcium fluoride,calcium phosphate, calcium carbonate, calcium hydroxide, and the likecan be preferably used as the material corresponding to calcium. Notethat two or more kinds selected from the above compound group may beused in combination.

Also, as described above, the dental glass according to the presentembodiment can contain optional components other than theabove-described components. For example, it is possible to contain oneor more kinds selected from strontium, lanthanum, boron, zinc, silver,fluorine, and the like. In a case where the dental glass according tothe present embodiment contains such optional components, the materialcomposition can contain materials corresponding to the optionalcomponents.

Although a material corresponding to strontium is not particularlylimited, for example, one or more kinds selected from strontiumfluoride, strontium hydroxide, strontium carbonate, strontium oxide,strontium phosphate, and the like can be preferably used as the materialcorresponding to strontium. Note that two or more kinds selected fromthe above compound group may be used in combination.

Although a material corresponding to lanthanum is not particularlylimited, for example, one or more kinds selected from lanthanumfluoride, lanthanum oxide, and the like can be preferably used as thematerial corresponding to lanthanum. Note that two or more kindsselected from the above compound group may be used in combination.

Although a material corresponding to boron is not particularly limited,for example, one or more kinds selected from boron oxide, borax, boronphosphate, and the like can be preferably used as the materialcorresponding to boron. Note that two or more kinds selected from theabove compound group may be used in combination.

Although a material corresponding to zinc is not particularly limited,for example, one or more kinds selected from zinc oxide, zinc fluoride,and the like can be preferably used as the material corresponding tozinc. Note that two or more kinds selected from the above compound groupmay be used in combination.

Although a material corresponding to silver is not particularly limited,for example, one or more kinds selected from silver oxide, silvernitrate, silver fluoride, and the like can be preferably used as thematerial corresponding to silver. Note that two or more kinds selectedfrom the above compound group may be used in combination.

Although a material corresponding to fluorine is not particularlylimited, for example, one or more kinds selected from calcium fluoride,strontium fluoride, sodium fluoride, and the like can be preferably usedas the material corresponding to fluorine. Note that two or more kindsselected from the above compound group may be used in combination.

The respective materials in a material composition may be mixed so as tocorrespond to the composition of a dental glass. For example, therespective materials can be weighed and mixed in accordance with thecomposition of the dental glass to prepare the material composition(material composition preparation step).

Then, the obtained material composition can be placed in, for example, acrucible, heated and fused at a temperature in accordance with themelting point of the materials or the like, for example, greater than orequal to 700° C. and less than or equal to 1500° C., and thereaftercooled (heating/cooling step).

Although the cooling rate at the time of cooling is not particularlylimited, for example, rapid cooling is preferable by various rapidcooling means such as a twin-roll process as described above or aprocess of pouring out the met onto a metal plate and pressing it.

After being cooled and solidified, the dental glass can be produced bypulverization to have a desired particle diameter (pulverizing step).

In addition to the above-described steps, the method of producing thedental glass according to the present embodiment may further includeoptional steps. For example, classification or the like can be carriedout such that the particle size distribution of the obtained dentalglass becomes a desired distribution.

EXAMPLES

Although specific Examples and Comparative Examples will be described inthe following, the present invention is not limited to the examples.

First, the evaluation methods of the dental glasses produced in thefollowing Examples and Comparative Examples will be described.

(Vitrification)

In each of the following Examples and Comparative Examples, a materialcomposition was prepared by mixing materials for a dental glass, theprepared material composition was heated and melted, and thereafterrapidly cooled to an ambient temperature to prepare the dental glass.Then, the state of each prepared dental glass was visually confirmed andevaluated as “GOOD” when vitrification was confirmed, and “POOR” when itwas not vitrified. Note that when it was not vitrified, it means that adental glass could not be prepared, and thus the subsequent evaluationwas not carried out.

(Solubility in Water)

The prepared dental glass was pulverized to prepare a pulverized glasshaving an average particle diameter of 10 μm. Subsequently, thepulverized glass is dispersed in distilled water to have a concentrationof 1% by mass (mass of charged dental glass), and the mixture is stirredat an ambient temperature for 1 hour. Next, undissolved glass powder wasrecovered with filter paper, and dried. Thereafter, the mass of theundissolved dental glass after being dried (undissolved dental glassmass) was measured, and the solubility of the dental glass in water wascalculated by the following formula (1).

(solubility of dental glass in water (mass %))=[(input dental glassmass)−(undissolved dental glass mass)]/(input dental glassmass)×100  Formula (1)

(pH after being Dissolved in Water)

The prepared dental glass was pulverized to prepare a pulverized glasshaving an average particle diameter of 10 μm. Next, a pH, after thepulverized glass was dispersed in distilled water so as to have aconcentration of 1% by mass and stirred at an ambient temperature for 1hour, was measured as the pH after being dissolved in water.

Example 1

Phosphoric acid, calcium phosphate, and sodium carbonate as materialswere weighed and mixed so as to have the composition indicated inTable 1. Then, the obtained mixture was placed in a platinum crucible,heated at 1100° C. in an air atmosphere and melted, then poured out on astainless steel plate and rapidly cooled by being pressed by an iron toproduce a dental glass.

Note that in Table 1, with respect to P, Na, K, Ca, Sr, B, Si, Al, La,Zn and Ag, the ratios in terms of oxides are indicated.

Example 2 to Example 8

Except that materials were weighed and mixed such that the dentalglasses had the compositions indicated in Table 1 for respectiveExamples, the dental glasses were prepared and evaluated similarly toExample 1.

The results are indicated in Table 1.

Comparative Example 1 to Comparative Example 9

Except that materials were weighed and mixed such that the dentalglasses had the compositions indicated in Table 1 for respectiveComparative Examples, the dental glasses were prepared and evaluatedsimilarly to Example 1.

The results are indicated in Table 1.

TABLE 1 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple ple ple pleple ple ple ple 1 2 3 4 5 6 7 8 COM- P₂O₅ 68.3 57.7 59.6 53.9 44.2 49.852.4 59.8 POSI- Na₂O 28.1 25.1 33.4 — 23.8 — 21.0 39.0 TION K₂O — — —32.1 — 33.0 — — OF CaO 3.6 5.3 1.0 4.3 6.4 2.2 3.4 1.2 DENTAL SrO — 10.3— 8.4 8.6 4.6 — — GLASS B₂O₃ — 1.6 — 1.3 — — 3.6 — (MASS %) SiO₂ — — — —— — — — Al₂O₃ — — — — — — — — La₂O₃ — — 4.5 17.0 — 17.5 — ZnO — — 1.5 —— 3.9 — — AgO — — — — — 6.5 — — F — — — — — — 2.1 — Fe — — — — — — — — S— — — — — — — — EVALUATION VITRIFI- GOOD GOOD GOOD GOOD GOOD GOOD GOODGOOD RESULTS CATION SOLUBILITY 78.0% 28.0% 88.0% 56.0% 21.0% 89.0% 15.0%100.0% IN WATER pH AFTER 7.3 7.5 8.7 7.0 8.4 6.8 8.4 9.6 BEING DISSOLVEDIN WATER Com- Com- Com- Com- Com- Com- Com- Com- Com- parative parativeparative parative parative parative parative parative parative Exam-Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple ple ple ple ple pleple ple ple 1 2 3 4 5 6 7 8 9 COM- P₂O₅ 73.7 68.7 35.4 42.6 47.5 67.053.1 6.6 50.1 POSI- Na₂O 21.8 — 33.8 — — 16.2 8.4 30.6 — TION K₂O — — —56.4 15.5 — — — 32.3 OF CaO 2.9 31.3 6.2 1.0 10.1 7.2 2.5 15.8 — DENTALSrO — — — — 26.9 — — — — GLASS B₂O₃ — — — — — 4.8 19.3 — — (MASS %) SiO₂— — — — — — — 47.0 — Al₂O₃ — — — — — — — — 11.4 La₂O₃ — — — — — — 9.6 —— ZnO 1.6 — — — — 4.8 — — 6.2 AgO — — — — — — 5.2 — — F — — 24.6 — — —1.9 — — Fe — — — — — — — — — S — — — — — — — — — EVALUATION VITRIFI-GOOD GOOD POOR POOR GOOD GOOD GOOD GOOD GOOD RESULTS CATION SOLUBILITY32.0% 8.0% — — 2.6% 7.1% 1.3% 2.4% 2.6% IN WATER pH AFTER 3.1 3.9 — —7.2 3.0 2.5 11.8 7.5 BEING DISSOLVED IN WATER

According to the results indicated in Table 1, it was confirmed that ineach of Example 1 to Example 8, the solubility in water was high andgreater than or equal to 10%. Accordingly, the dental glasses could beconfirmed as being excellent in a property of releasing ions such ascalcium ions and phosphate ions contained in the dental glasses for therespective Examples. Also, the pH after being dissolved in water was ina range of greater than or equal to 5 and less than or equal to 11, andthe dental glasses could be confirmed as being applicable into a mouth.

In contrast, Comparative Example 2 and Comparative Examples 5 to 9 hadthe solubility in water less than 10%, and could be confirmed as nothaving a sufficient solubility in water. Therefore, the dental glassescould be confirmed as being inferior in a property of releasing ionssuch as calcium ions and phosphate ions.

Also, in Comparative Example 1, although the solubility in water was 32%and high, the pH after being dissolved in water was 3.1 and very low,Comparative Example 1 could be confirmed as not being applicable into amouth.

In Comparative Examples 3 and 4, vitrification could not be confirmed.That is, dental glass could not be obtained.

Although dental glasses and dental compositions have been describedabove with reference to the embodiment, the examples, etc., the presentinvention is not limited to the embodiments, the examples, etc.described above. Various modifications and changes can be made withinthe scope of the present invention recited in the claims.

1. A dental glass comprising, in terms of oxide: phosphorus (P₂O₅) bygreater than or equal to 40% by mass and less than or equal to 70% bymass; potassium (K₂O) by greater than or equal to 20% by mass and lessthan or equal to 40% by mass; and calcium (CaO) by greater than or equalto 1% by mass and less than or equal to 20% by mass, wherein the dentalglass does not substantially contain silicon and aluminum.
 2. A dentalcomposition comprising the dental glass according to claim 1.